Female Athlete Knee Injury Kelly C. McInnis, DO Physical Medicine and Rehabilitation Massachusetts General Hospital Sports Medicine Center Outline Historical Perspective Gender-specific movement patterns Knee Injury Anterior Cruciate Ligament Injury Patellofemoral Pain Prevention Programs Future Directions Participation in Sport 4,000,000 3,000,000 2,000,000 Boys Girls 1,000,000 0 1971 1984 2006 Title IX Equal Opportunity in Education Act 1
Benefits of Sport Higher graduation rates Fewer unwanted pregnancies Greater self esteem Team, leadership Decrease risk of chronic illness Heart disease Diabetes Osteoporosis Gender Differences Cardiovascular Smaller heart Cardiac output 30% less than equally trained male 10-15% less hemoglobin, 6% less rbc s Pulmonary Smaller chest wall Less vital capacity Dec VO2 max MSK Growth spurt earlier Less lean body mass, dec strength, power, speed Endocrine Anatomic Differences Limb length Articular surface Flexibility / ligament laxity % Muscle / % Fat Thigh mm development Static alignment Wider pelvis Femoral anteversion Genu valgum Narrow notch External tibial rotation Foot pronation Narrower shoulders Lower COG. 2
Dynamic Alignment Landing Mechanics Step Down Courtesy of Luke Oh, MD MGH Sports Medicine 3
Single Leg Squat Drop Jump Dominant Movement Pattern Core instability Hip adduction / internal rotation Tibial external rotation Navicular Drop / Foot pronation In toe or Out toe Apparent knee valgus 4
Female Athlete Injuries Acute Anterior Cruciate Ligament Injury Patellar subluxation / dislocation Overuse Patellofemoral Pain Greater Trochanteric Pain Syndrome Iliotibial Band Syndrome Medial Tibial Stress Syndrome Stress Fracture Knee Injury Rates NCAA Injury Surveillance System. 1997-1998. Anterior Cruciate Ligament Injury 80,000 250,000 annual incidence 70% noncontact 50% age 15-25 yo Females 2 81 Females 2-8:1 Sport-specific Soccer, basketball 5
Impact of ACL Injury Cost 100,000 reconstructions annually Time lost from work, school, sports Natural history Post-traumatic degenerative disease 1/10 re-injury rate Mechanism of Injury Landing Straight knee 28% Deceleration Planting and cutting 29% One-step stop w/ knee hyperext 26% Unexpected perturbation Relative knee / hip extension, knee abduction w/ foot pronation Axial load 6
In Vivo ACL Biomechanics High strain Near full extension Quadricep ctx or isometric hamstring ctx Low strain < 50 deg KF Hamstring or isometric quadricep ctx Beynnon BD and Fleming et al. The measurement of anterior cruciate ligament strain in vivo. J Biomech.1992. 7
Female ACL Injury What Gives? Multifactorial Environmental Anatomic Hormonal Neuromuscular Anatomic Factors Knee valgus Foot pronation BMI Femoral notch properties Notch width Notch shape ACL mechanical quality Joint Laxity Hypermobility Musculotendinous flexibility Genu recurvatum can delay hamstring activation Posterior tibial slope Anterior tibial translation Mixed studies for injury risk 8
Hormonal Factors Estrogen, progesterone, relaxin receptors on ACL fibroblasts Estrogen reduces collagen synthesis High levels ligament laxity muscle fatigability Estrogen highest in pre-ovulatory phase Yu et al. CORR. 2001. Hormonal Factors Wojtys et al. AJSM. 2002. Hewett et al. AJSM. 2007. Postovulatory Preovulatory 9
Oral Contraceptives 42-70% collegiate female athletes Blunt cyclic hormonal fluctuations May increase passive and dynamic knee stability May lower injury risk Mixed studies Conclusion Hormonal differences likely contribute to risk for ACL injury No direct relationship b/t specific hormone fluctuation and injury Neuromuscular Factors Movement Patterns Landing mechanics Core instability Hip: Less HF, Dec gluteal firing Hip: Less HF, Dec gluteal firing Knee: Less KF, valgus Foot: pronation velocity, less PF Increase ground reaction force 10
Weak Link in Kinetic Chain Neuromuscular Factors Movement Patterns Leg dominance Balance, proprioception Fatigue Exaggerates pattern Male and female Increased proximal tibial anterior shear force Quadriceps Dominance Quadriceps dominant ctx In vivo analysis higher ACL strain Eccentric ctx anterior Eccentric ctx, anterior translation of tibia Hamstring activation during landing / pivoting may be protective Medial quadriceps relative weakness 11
Bottom Line Posterior Kinetic Chain Weakness Shorter activation of muscles that maintain knee stiffness Gastrocnemius Gluteus maximus, medius, minimus -- Hamstring Single leg stance, squat ACL Injury Prevention Programs Do They Really Work? Prevention Premise Epidemiology Target young female Understand Mechanism of Injury f Identify Risk Factors Implementation Compliance 12
AJSM. 2006. ACL Prevention Programs Several neuromuscular programs proposed Preseason vs In season Frequency and duration of training Various sports Soccer, handball, volleyball, basketball Most prospective, nonrandomized Athlete compliance Encouraging results DiStefano et al. AJSM. 2009. 13
Anterior Cruciate Ligament Injuries in Female Athletes Part 2, A Meta-analysis of Neuromuscular Interventions Aimed at Injury Prevention Hewett et al. AJSM. 2006 AJSM. 2008. Study Design 61 NCAA Div 1 soccer teams, 1435 athletes t Intervention group: PEP 3X/wk during 2002 season Control group: own customary warm up Results Overall 41% reduction in ACL 18:7 Noncontact 70% reduction 10:2 Significance: decrease in reinjury, late season injury 14
Decrease Risk of ACL Injury Numbers Needed to Treat = 89 to Prevent 1 ACL Injury Risk Reduction of other Injuries? Patellofemoral Pain Peritrochanteric Pain LE Stress Fracture Performance Enhancement Patellofemoral Pain Females 2:1 Overuse Injury Pain generator controversial Imbalanced forces controlling patellar tracking, jt overload Static stabilizers Dynamic stabilizers Peripatellar pain; down stairs, prolonged sitting Patellofemoral Pain Risk Factors Training errors Increased Q angle / valgus Normal Q angle < 20 Ligamentous laxity Patellar hypermobility Genu recurvatum Foot pronation 15
A prospective investigation of biomechanical risk factors for patellofemoral pain syndrome. Boling MC et al. AJSM. 2009. Decreased KF angle Decreased vertical ground reaction force Increased hip internal rotation angle Decreased quad and hamstring strength Increased navicular drop No single biomechanical factor has been consistently shown to reliably predict the presence or outcome of PFS Patellofemoral Pain Evaluate entire kinetic chain Dynamic alignment Single-leg squat Lateral cutting Jumping Running Strength / Flexibility Hip Adb / ER Core Quad, hamstring, ITB Foot/Ankle Ireland ML and Nattiv A. The Female Athlete. Saunders. 2002. Dynamic Testing 16
Treatment: Table Out Individualized Program Activity modification NSAID, brace, tape, orthotics Physical Therapy Correct dynamic imbalances Quad strengthening Core, hip stabilization Stretching Motor retraining Skill acquisition Surgical Myth of the VMO Can vastus medialis oblique be preferentially activated? Systematic review; Smith et al. Physiother Theory Pract. Feb 2009. Limb-joint i orientation ti Muscular co-contraction EMG studies reveal insufficient data Do the VMO and VML really exist? Systematic review; Smith et al. Clin Anat. Mar 2009. Insufficient evidence to suggest 2 separate components of VM exist Patellofemoral Pain Prevention Program Correct dynamic imbalances Core strengthening / stabilization Hip Abduction / ER strengthening Hip Abduction / ER strengthening Quad strengthening Balanced stretching Motor retraining 17
Summary Female athletes are target Dominant movement patterns Importance of kinetic chain Neuromuscular control, motor retraining Prevention may be best treatment Future Directions Neuroplasticity Transcranial magnetic stimulation, fmri Landing Error Scoring System Identify female high h risk pattern Individualized programs Prevention / postoperative PT training Preparticipation examination Dissemination / Compliance Thank You 18
17 ACL def > 6 mo, 18 ACL intact dominant legs Brain activation patterns using fmri Results ACL def Decreased activation in several sensorimotor cortical areas, increased activation in 3 areas Conclusion ACL def can cause reorganization in CNS Neurophysiologic dysfuntion not just periph msk New standards in rehab and motor relearning 19